The present invention generally relates to an I/O control device and an I/O control method, and particularly to an I/O control device and an I/O control method for transferring data.
A system exists for transferring data residing in one place to another remote domain. In such a system, the I/O instruction is managed upon the transferring of data.
Here, the manageable I/O instruction is determined and controlled according to the storage capacity of the memory.
FIG. 1 is a block diagram showing an example of a conventional remote copy system. The remote copy system 1 is composed of a host computer 2, an I/O control device 3, a storage device 4, and a circuit control mechanism 5.
The host computer 2 issues I/O commands, transfers data, and the like. The I/O control device 3 is connected between the host computer, the device 4, and the circuit control mechanism 5, and controls the input/output of data according to the I/O instruction.
The device 4 is a storage device such as a hard disk and the like. The circuit control mechanism 5 is connected to circuit 6.
The I/O control device 3 is mainly composed of a channel adapter 11, a device adapter 12, a remote adapter 13, a control unit 14, and a transfer control information table 15.
The channel adapter 11 is a device for establishing communication with the host computer 2. The device adapter 12 is a device for establishing communication with the device 4. The remote adapter 13 is a device for establishing communication with the circuit control mechanism 5.
The control unit 14 controls the transfer of data based on the I/O instruction from the host computer 2. The transfer control information table 15 is a table that contains the transfer control information.
Now, the operation of the conventional remote copy system shall be explained.
The I/O instruction for executing a remote copying operation is supplied from the host computer 2 to the I/O control device 3. The I/O instruction is first supplied to the channel adapter 11. Upon receiving the I/O instruction from the host computer 2, the channel adapter 11 communicates the received I/O instruction to the control unit 14.
Upon receiving the I/O instruction, the control unit 14 establishes a transfer control information table 15 for storing transfer control information into the memory of the I/O control device. The transfer control information table 15 establishes a pre-set and predetermined storage domain. The transfer control information is stored in the transfer control information table 15.
FIG. 2 illustrates an exemplary data composition diagram of the conventional transfer control information.
Transfer control information 20 comprises control classification information 21, update range information 22, transfer track information 23, write classification information 24, update range information 25, and error information 26.
The control classification information 21 indicates the type of I/O instruction. Such information is used, for example, to identify whether the instruction is for a simple update or a remote transfer. The update range information 22 indicates the update range.
The transfer track information 23 designates the transfer track. The write classification information 24 identifies the write type. For example, it is used in order to identify whether the write type is a format write or an update write.
The update range information 25 designates the update range. For instance, it designates the start and end of the information. The error information 26 indicates whether or not an error has occurred.
The control unit 14 reads the data on the track which is to be transferred from device 4 based on the transfer control information stored in transfer control information table 15, and supplies this to the remote adapter 13. The remote adapter 13 supplies the data from the control unit 14 to the circuit control mechanism 5. The circuit control mechanism 5 supplies this to other devices via circuit 6.
The above is a description of a remote copying operation.
However, in the above remote copying operation, the amount of data for which the remote copying operation can be performed at one time with the I/O instruction is limited according to the storage capacity of the transfer control information table 15. Therefore, for transferring a large volume of transfer data, it is necessary to perform the transfer by segmenting the I/O instruction.
The object of the present invention is to enable the transfer of data, which does not impose a limitation to the amount of data to be transferred.
The present invention detects the processed state of the transfer control information stored in the transfer control information memory means, and upon completion of transfer control information-dependent transfer processing as a result of the state detection, stores new transfer control information in the transfer control information memory means in place of the above transfer control information.
According to the present invention, the transfer control information can be established without taking into account the limitation of the capacity of the transfer control information memory means though it may have a fixed capacity. Thus, even small devices with a relatively small memory capacity will be able to provide functions similar to that of bigger devices without any demerits whatsoever.
Also, upon detecting an error state in the processing corresponding to the transfer control information, the present invention leaves that transfer control information stored in the transfer control information memory means.
According to the present invention, the transfer control information having an error detected therein will be stored as it is so that the cause of the error may be investigated by examining the stored transfer control information.